This invention relates in general to anesthestic devices and in particular a new and useful device for facilitating the puncture of a person's tissue for the purpose of administering an anesthetic.
The invention concerns a combination needle for axillary plexus brachialis anesthesia, consisting of a plastic tube and a cylindrical steel mandrel with a handle and a partially ground puncturing tip, which can be inserted into the plastic tube so that its puncturing tip extends through the front end of the plastic tube.
A plexus brachialis block in the axillary area is preferred for anesthesia and analgesia of the arm. Known for this purpose is a combination needle of this type (Regional-Anasthesia 6: 43-46, 1983). This combination consists of a hollow, i.e. tubular or cannula-like steel mandrel with a sharp tip ground at an angle of less than 45.degree. and equipped with lateral facets (Crawford grinding) as well as a plastic tube of polytetrafluoroethylene, into which the hollow steel mandrel can be inserted in such a way that its ground tip extends through the front end of the plastic tube.
For the puncturing, this combination needle with the hollow, sharp tip extending through the front end of the plastic tube is advanced first until the steel mandrel's tip touches the nerve sheat (neurovascular fascia) of the axillary plexus brachialis nerve. Then, the nerve sheath is punctured with the steel mandrel, and the plastic tube is advanced into the nerve sheath along the steel mandrel. The steel mandrel is then retracted from the plastic tube. An anesthetic can then be injected through the empty plastic tube. The introduction of a thin, flexible catheter through the plastic tube lying in the nerve sheath is also possible.
After puncturing, the resistance of the tissue to the advancing steel mandrel's tip during the advancing of the needle is low up to the nerve sheath. But as soon as the point of the steel mandrel touches the nerve sheath, a perceptibly greater resistance is felt immediately, which decreases instantly, however, at the moment when the nerve sheath is punctured again. This change in resistance to the advancing needle can be used to check the exact location of the needle. This is possible only to a limited extent with the known needle since it has a sharp tip with sharp cutting edges, which strongly reduces the perceptibility of the change in resistance. This is not the only reason for attaching to the shaft, of the steel mandrel of the known combination needle, a syringe with physiological saline solution, to make the resistance to the advancing needle noticeable also as a piston pressure at the syringe. But the syringe attached to the steel mandrel makes the handling of the known needle cumbersome and difficult. The laterally partially ground facets at the hollow tip of the steel mandrel produce a sharp tip, despite the angle of grinding of 45 .degree., which is greater than that of conventional needles, as well as in laterally extending sharp cutting edges that facilitate the puncturing of the nerve sheath but make the danger of damage to nerves and vessels unavoidable. Finally, the laterally ground facets with their cutting edges at the hollow steel mandrel's cause a certain punching or cutting off action during the insertion of the combination needle with the hollow mandrel, which has the consequenc that infected skin components or deeper lying tissue particles can be carried further down and cause infections.